Incidence and prevalence of large vessel vasculitis (giant cell arteritis and Takayasu arteritis) in northern Italy: A population-based study.

Objectives: To investigate the epidemiology of the entire spectrum of large vessel vasculitis (LVV) in a well-defined population from a Northern Italian area.

Methods: All patients with incident giant cell arteritis (GCA) diagnosed from 2005 to 2016 and all patients with incident Takayasu arteritis (TAK) diagnosed from 1998 to 2016 living in the Reggio Emilia area were identified. Only patients satisfying the modified inclusion criteria of the GiACTA trial, and the 1990 ACR classification criteria for TAK were included. The epidemiology of cranial- and LV-GCA was separately evaluated.

Results: 207 patients were diagnosed with GCA and 5 with TAK. 123 patients had cranial-GCA, 53 patients had LV-GCA, and the remaining 31 patients had overlapping features. The standardized annual incidence rate of GCA was 8.3 (95% CI 7.1, 9.4) per 100,000 population ages ≥50 years. The standardized annual incidence rate of cranial-GCA (6.1 [95% CI 5.1, 7.1] per 100,000 population ages ≥50 years) was double the rate of LV-GCA (3.4 [95% CI 2.7, 4.2]). The age-specific incidence rates were similar in the <70 and >90 years age groups, but they were higher in cranial-GCA than in LV-GCA in the age groups 70-79 and 80-89 years. The age- and sex-adjusted annual incidence rate of TAK was 0.5 (95% CI 0.1, 1.2) per 1,000,000 population.

Conclusion: Incidence of GCA is higher than previously reported by study evaluating only biopsy-proven or ACR classification criteria confirmed cases. Cranial-GCA and LV-GCA have epidemiological differences. TAK is an extremely rare disease also in Italy.